1. Field of the Invention:
This invention relates to a plug assembly and, in particular, to a puncture plug assembly adapted to permit an opening of a medical instrument, such as a retention needle and catheter, to be temporarily closed and to permit a fluid medicament to be injected through an injection needle into a human body, or to permit a body fluid, such as blood, to be taken from the human body, with the instrument being closed by the plug assembly.
2. Description of the Prior Art:
During the application of anesthesia, the transfusion of a liquid medicament and blood, the blood pressure measurement and the extracorporeal blood circulation, it is often required that a patient be moved from room to room of a hospital and from hospital to hospital and it is also required that an operation or treatment be temporarily interrupted. In this situation it will be necessary to retain or hold a needle or catheter in the blood vessel of the patient. At this time, use is made of a rubber plug assembly for puncture, in which a puncturable rubber is fitted over a rigid plug assembly, or a plug assembly for puncture in which a rubber plug is forced into a rigid plug body. It is often required that a liquid medicament such as a heparinized physiological sodium chloride solution be injected by, for example, an injection needle, as required, through the rubber with the plug assembly fitted into the base of a retention needle or a catheter.
FIG. 1 shows one example of a conventional plug assembly for puncture. This plug assembly comprises a plug body 1 and a rubber 2 for puncture. The plug assembly 1 has a double-walled cylinder section (3, 4) at a forward one-half section and a single-walled cylinder section at a rear one-half section 5. The puncture rubber 2 has a double-walled cylinder section (6, 7) coaxial with the plug body 1, and the cylinder section (6, 7) is covered over the plug body 1. The section 5 of the plug body 1 is fitted in a space between the walls 6 and 7 of the section (6, 7) so as to be held by a frictional resistance.
In the above-mentioned conventional plug assembly, however, a body fluid etc. are liable to be penetrated in a possible gap between the plug body 1 and the rubber 2 and, if this occurs, the frictional resistance therebetween is decreased due to the penetration of the body fluid. When, therefore, the injection needle penetrated into the rubber plug 2 is withdrawn from the plug assembly, the injection needle toegether with the rubber falls off, or if this is not the case a gap is created between the plug body 1 and the rubber 2, causing a fluid leakage.